read/pe: support all export types (#349)

PE exports can be either:
* forwarded to another DLL
* in the current PE file

Additionally, each of them can either:
* have a name (and an ordinal)
* have only an ordinal

src/read/mod.rs

@@ -460,7 +460,7 @@ impl<'data> Import<'data> {
 /// An exported symbol.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct Export<'data> {
-    // TODO: and ordinal?
+    // TODO: and ordinal
     name: ByteString<'data>,
     address: u64,
 }

src/read/pe/export.rs

@@ -0,0 +1,152 @@
+use alloc::vec::Vec;
+use core::convert::TryInto;
+use core::fmt::Debug;
+
+use crate::read::ReadError;
+use crate::read::Result;
+use crate::ByteString;
+use crate::{pe, Bytes, LittleEndian as LE, U16Bytes, U32Bytes};
+
+/// Where an export is pointing to
+#[derive(Clone)]
+pub enum ExportTarget<'data> {
+    /// The export points at a RVA in the file
+    Local(u64),
+    /// The export is "forwarded" to another DLL
+    ///
+    /// for example, "MYDLL.expfunc" or "MYDLL.#27"
+    Forwarded(&'data [u8]),
+}
+
+/// An export from a PE file
+///
+/// There are multiple kinds of PE exports (with or without a name, and local or exported)
+#[derive(Clone)]
+pub struct Export<'data> {
+    /// The ordinal of the export
+    pub ordinal: u32,
+    /// The name of the export, if ever the PE file has named it
+    pub name: Option<&'data [u8]>,
+    /// The target of this export
+    pub target: ExportTarget<'data>,
+}
+
+impl<'a> Debug for Export<'a> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::result::Result<(), core::fmt::Error> {
+        f.debug_struct("Export")
+            .field("ordinal", &self.ordinal)
+            .field("name", &self.name.map(ByteString))
+            .field("target", &self.target)
+            .finish()
+    }
+}
+
+impl<'a> Debug for ExportTarget<'a> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::result::Result<(), core::fmt::Error> {
+        match self {
+            ExportTarget::Local(addr) => f.write_fmt(format_args!("Local({:#x})", addr)),
+            ExportTarget::Forwarded(forward) => {
+                f.write_fmt(format_args!("Forwarded({:?})", ByteString(forward)))
+            }
+        }
+    }
+}
+
+impl<'data, Pe, R> super::PeFile<'data, Pe, R>
+where
+    Pe: super::ImageNtHeaders,
+    R: crate::ReadRef<'data>,
+{
+    /// Returns the exports of this PE file
+    ///
+    /// See also the [`PeFile::exports`] function, which only returns a subset of these exports.
+    pub fn export_table(&self) -> Result<Vec<Export<'data>>> {
+        let data_dir = match self.data_directory(pe::IMAGE_DIRECTORY_ENTRY_EXPORT) {
+            Some(data_dir) => data_dir,
+            None => return Ok(Vec::new()),
+        };
+        let export_va = data_dir.virtual_address.get(LE);
+        let export_size = data_dir.size.get(LE);
+        let export_data = data_dir.data(self.data, &self.common.sections).map(Bytes)?;
+        let export_dir = export_data
+            .read_at::<pe::ImageExportDirectory>(0)
+            .read_error("Invalid PE export dir size")?;
+        let addresses = export_data
+            .read_slice_at::<U32Bytes<_>>(
+                export_dir
+                    .address_of_functions
+                    .get(LE)
+                    .wrapping_sub(export_va) as usize,
+                export_dir.number_of_functions.get(LE) as usize,
+            )
+            .read_error("Invalid PE export address table")?;
+        let number = export_dir.number_of_names.get(LE) as usize;
+        let names = export_data
+            .read_slice_at::<U32Bytes<_>>(
+                export_dir.address_of_names.get(LE).wrapping_sub(export_va) as usize,
+                number,
+            )
+            .read_error("Invalid PE export name table")?;
+        let base_ordinal = export_dir.base.get(LE);
+        let ordinals = export_data
+            .read_slice_at::<U16Bytes<_>>(
+                export_dir
+                    .address_of_name_ordinals
+                    .get(LE)
+                    .wrapping_sub(export_va) as usize,
+                number,
+            )
+            .read_error("Invalid PE export ordinal table")?;
+
+        // First, let's list all exports...
+        let mut exports = Vec::new();
+        for (i, address) in addresses.iter().enumerate() {
+            // Convert from an array index to an ordinal
+            // The MSDN documentation is wrong here, see https://stackoverflow.com/a/40001778/721832
+            let ordinal: u32 = match i.try_into() {
+                Err(_err) => continue,
+                Ok(index) => index,
+            };
+            let ordinal = ordinal + base_ordinal;
+            let address = address.get(LE);
+
+            // is it a regular or forwarded export?
+            if address < export_va || (address - export_va) >= export_size {
+                exports.push(Export {
+                    ordinal: ordinal,
+                    target: ExportTarget::Local(
+                        self.common.image_base.wrapping_add(address as u64),
+                    ),
+                    name: None, // might be populated later
+                });
+            } else {
+                let forwarded_to = export_data
+                    .read_string_at(address.wrapping_sub(export_va) as usize)
+                    .read_error("Invalid target for PE forwarded export")?;
+                exports.push(Export {
+                    ordinal: ordinal,
+                    target: ExportTarget::Forwarded(forwarded_to),
+                    name: None, // might be populated later
+                });
+            }
+        }
+
+        // Now, check whether some (or all) of them have an associated name
+        for (name_ptr, ordinal_index) in names.iter().zip(ordinals.iter()) {
+            // Items in the ordinal array are biased.
+            // The MSDN documentation is wrong regarding this bias, see https://stackoverflow.com/a/40001778/721832
+            let ordinal_index = ordinal_index.get(LE) as u32;
+
+            let name = export_data
+                .read_string_at(name_ptr.get(LE).wrapping_sub(export_va) as usize)
+                .read_error("Invalid PE export name entry")?;
+
+            exports
+                .get_mut(ordinal_index as usize)
+                .ok_or_else(|| crate::read::Error("Invalid PE export ordinal"))?
+                .name = Some(name);
+        }
+
+        Ok(exports)
+    }
+}

src/read/pe/file.rs

@@ -9,9 +9,7 @@ use crate::read::{
     self, Architecture, ComdatKind, Error, Export, FileFlags, Import, NoDynamicRelocationIterator,
     Object, ObjectComdat, ReadError, ReadRef, Result, SectionIndex, SymbolIndex,
 };
-use crate::{
-    pe, ByteString, Bytes, CodeView, LittleEndian as LE, Pod, U16Bytes, U32Bytes, U32, U64,
-};
+use crate::{pe, ByteString, Bytes, CodeView, LittleEndian as LE, Pod, U32, U64};
 
 use super::{PeSection, PeSectionIterator, PeSegment, PeSegmentIterator, SectionTable};
 
@@ -297,60 +295,21 @@ where
     }
 
     fn exports(&self) -> Result<Vec<Export<'data>>> {
-        let data_dir = match self.data_directory(pe::IMAGE_DIRECTORY_ENTRY_EXPORT) {
-            Some(data_dir) => data_dir,
-            None => return Ok(Vec::new()),
-        };
-        let export_va = data_dir.virtual_address.get(LE);
-        let export_size = data_dir.size.get(LE);
-        let export_data = data_dir.data(self.data, &self.common.sections).map(Bytes)?;
-        let export_dir = export_data
-            .read_at::<pe::ImageExportDirectory>(0)
-            .read_error("Invalid PE export dir size")?;
-        let addresses = export_data
-            .read_slice_at::<U32Bytes<_>>(
-                export_dir
-                    .address_of_functions
-                    .get(LE)
-                    .wrapping_sub(export_va) as usize,
-                export_dir.number_of_functions.get(LE) as usize,
-            )
-            .read_error("Invalid PE export address table")?;
-        let number = export_dir.number_of_names.get(LE) as usize;
-        let names = export_data
-            .read_slice_at::<U32Bytes<_>>(
-                export_dir.address_of_names.get(LE).wrapping_sub(export_va) as usize,
-                number,
-            )
-            .read_error("Invalid PE export name table")?;
-        let ordinals = export_data
-            .read_slice_at::<U16Bytes<_>>(
-                export_dir
-                    .address_of_name_ordinals
-                    .get(LE)
-                    .wrapping_sub(export_va) as usize,
-                number,
-            )
-            .read_error("Invalid PE export ordinal table")?;
-
-        let mut exports = Vec::new();
-        for (name, ordinal) in names.iter().zip(ordinals.iter()) {
-            let name = export_data
-                .read_string_at(name.get(LE).wrapping_sub(export_va) as usize)
-                .read_error("Invalid PE export name entry")?;
-            let address = addresses
-                .get(ordinal.get(LE) as usize)
-                .read_error("Invalid PE export ordinal entry")?
-                .get(LE);
-            // Check for export address (vs forwarder address).
-            if address < export_va || (address - export_va) >= export_size {
-                exports.push(Export {
-                    name: ByteString(name),
-                    address: self.common.image_base.wrapping_add(address.into()),
-                })
+        self.export_table().map(|pe_exports| {
+            let mut exports = Vec::new();
+            for pe_export in pe_exports {
+                match (pe_export.name, pe_export.target) {
+                    (Some(name), super::export::ExportTarget::Local(address)) => {
+                        exports.push(Export {
+                            name: ByteString(name),
+                            address,
+                        })
+                    }
+                    _ => continue,
+                }
             }
-        }
-        Ok(exports)
+            exports
+        })
     }
 
     fn pdb_info(&self) -> Result<Option<CodeView>> {

src/read/pe/mod.rs

@@ -13,4 +13,7 @@ pub use file::*;
 mod section;
 pub use section::*;
 
+mod export;
+pub use export::*;
+
 pub use super::coff::{SectionTable, SymbolTable};

src/read/traits.rs

@@ -166,7 +166,9 @@ pub trait Object<'data: 'file, 'file>: read::private::Sealed {
     /// Get the imported symbols.
     fn imports(&self) -> Result<Vec<Import<'data>>>;
 
-    /// Get the exported symbols.
+    /// Get the exported symbols that expose both a name and an address.
+    ///
+    /// Some file formats may provide other kinds of symbols, that can be retrieved using the lower-level API
     fn exports(&self) -> Result<Vec<Export<'data>>>;
 
     /// Return true if the file contains debug information sections, false if not.